Deposition of Electroactive Polymers onto Polymer Nanofibers for Nerve Regeneration
Santiago, Marvin D.
Although peripheral nerves can regenerate after an injury through the Wallerian degeneration process, the degree of regeneration is often not efficient enough to achieve full return of functionality. To overcome the disadvantages of current nerve repair approaches, peripheral nerve tissue engineering strategies have been proposed by developing synthetic graft alternatives for long-gap nerve injuries. Nerve tissue engineering approach relies on mimicking the microenvironment of nerve tissue. This study reports the successful fabrication of an alternative for nerve tissue engineering. Electrospinning of the biocompatible polymer polycaprolactone (PCL) is used to produce porous and ordered nanofibers that resemble the structure and organization of the extracellular matrix, providing a suitable environment to promote the adhesion and directional growth of nerves. These oriented nanofibers are conformally coated with the inherently conducting polymer (ICP) polypyrrole (PPy) to provide an electrically conductive medium enabling the application of external stimuli to enhance cellular growth and connectivity. Furthermore, the scaffold is engineered with magnetic nanoparticles (MNPs) to provide a remote-controlled option for the delivery of electrical inputs through the generation of eddy currents when exposed to alternating magnetic fields. The biocompatibility of the fabricated composite has been proven using C2C12 and ND7/23 mouse cells. The growth of these cells has been shown to coincide with the alignment of the nanofibers. On highly aligned composites, there is evidence of neuroblastoma differentiation. While adhesion of the PPy coating onto the electrospun polymer has been demonstrated to be strong by tape test, it can potentially be enhanced by the formation of covalent bonds between the electrospun substrate and the modifier ICP. This study also preliminarily reports the success of reacting modified monomers of poly(3,4-ethylenedioxythiophene) (PEDOT) onto polyacryonitrile (PAN) and poly(methyl methacrylate) (PMMA). Aminomethyl EDOT (EDOT-MeNH2) was potentially successfully grafted onto PAN, alkaline hydrolyzed PAN , and PMMA. Hydroxymethyl EDOT (EDOT-MeOH) was also potentially successfully grafted onto alkaline hydrolyzed PAN. These would then be polymerized on the electrospun substrates, forming graft copolymers. The results of this study not only provide the foundations for a device for enhanced nerve regeneration, but also would be an enabling technology for the fabrication of improved composites of electrospun polymers and ICPs with applications in biomedical engineering and, potentially, energy storage, water purification, sensors, and wearable electronics.
Electroactive polymers, Inherently conducting polymers, Polymer nanofibers, Electrospinning, Polymer coatings, Nerve regeneration, Graft copolymerization, Polymer modification, Electrospun polymer modification
Santiago, M. D. (2022). <i>Deposition of electroactive polymers onto polymer nanofibers for nerve regeneration</i> (Unpublished thesis). Texas State University, San Marcos, Texas.